Client/serve systems, such as off-load servers, are often used in large scale computing environments. Customers for these systems, such as banks and credit card issuers, need high speed connectivity between their servers and mainframe systems to provide quality service and maximize their investment in information management. Applications that require such high speed connectivity include transaction co-processing, massive file transfers for decision support, archival databases for disaster recovery and transaction reporting requirements.
Non-IBM Plug Compatible Mainframe ("POM") systems need high speed inter connectivity to IBM PCM systems. Traditionally, this connectivity has been accomplished via data communications circuits and/or LAN connectivity that both systems share in common. However, customers have been demanding higher bandwidth connectivity. Unfortunately, data communications circuits and/or LANs share the deficiencies of relatively slow data rates, small blocksizes (which incur additional overhead too because of the larger number of blocks required to transmit the date), and the store and forward of data through network elements. Currently, to increase bandwidth, customers add additional circuits and the associated hardware and, in most cases, additional hardware is expensive front end processors ("FEPs"). Additionally, customers have legacy applications formed around this connectivity.
For conventional systems, the interactive interface between the server system and the mainframe system is restricted to homogeneous clusters of mainframe or mainframe plug compatible computers, particularly for IBM mainframe computers. IBM does provide channel-to-channel connectivity using TCP/IP to their series RS/6000 systems and Synchronous Network Architecture (SNA) to their series AS4. However, these systems do not provide for heterogeneous coupling of server systems from other vendors to mainframe systems.
The industry standard Small Computer System Interface (SCSI) has been used by conventional connectivity schemes to connect server systems to mainframe systems so that data may be transferred therebetween. Such connectivity schemes connect an input/output channel of a mainframe system to a SCSI interface of a server system. Thus, the industry standard SCSI interface provides for heterogeneous, physical coupling of server systems to mainframe systems. For example, the Data Blaster by Bus-Tech Inc. of Burlington, Mass., connects an IBM, IBM compatible and Unisys 2000 mainframe system to the SCSI interface of a server system and utilizes a simplistic virtual tape protocol to move data between the systems. During operation, the mainframe reads and writes to the Data Blaster as if it were a 3420 tape, and the server system reads and writes to the Data Blaster as if it were a standard SCSI attached tape.
However, the above conventional connectivity scheme does not operate in a network of computer systems. In addition, this conventional connectivity scheme uses the virtual tape protocol and does not interoperate with standard networking software. The above-noted Data Blaster emulates a standard tape controller on each side of the connection, and data is transferred using standard tape drive commands. Thus, the bulk data transfer is unidirectional and, thus, data can only be transferred in one direction at a time. Therefore, the above connectivity schemes merely permit file transfers and do not provide interactive operation between the server system and the mainframe system.
Against the foregoing background, it is a primary object of the present invention to provide a connectivity scheme that provides mainframe systems, particularly non-IBM and non-IBM plug compatible systems, with the virtual appearance of being a peer, vis-a-vis IBM systems, in a channel-to-channel network.
It is another object of the present invention to provide such a connectivity scheme that permits mainframe systems to communicate over high speed interfaces using large block sizes for a channel-to-channel network.
It is a further object of the present invention to provide such a connectivity scheme that allows mainframe systems to communication with each other using a standard interoperable protocol, such as the channel-to-channel protocol that is commonly used by IBM and IBM plug compatible mainframe systems.
It is also an object of the present invention to provide such a connectivity scheme to non-IBM and IBMPCMs via standard widely adopted interfaces such as Server Net, SCSI, PCI, ISA, Fibre Channel, ATM, EISA, and MCA, VME, S-BUS.